1. Technical Field
The present invention relates to a wavelength tunable interference filter, an optical filter device, an optical module, and an electronic apparatus.
2. Related Art
A wavelength tunable interference filter that extracts light with a predetermined wavelength from incident light is known (for example, refer to JP-A-2003-185941).
The Fabry-Perot filter (wavelength tunable interference filter) disclosed in JP-A-2003-185941 includes a fixed substrate and a movable substrate disposed opposite the fixed substrate with a spacer interposed therebetween, and a fixed mirror is provided on the fixed substrate and a movable mirror is provided on the movable substrate. In addition, the movable substrate includes a diaphragm and a protruding portion surrounded by the diaphragm, and the movable mirror is disposed in the protruding portion. In addition, in the wavelength tunable interference filter, a configuration is adopted in which the size of a gap between the fixed mirror and a reflector is changed by bending a diaphragm of the movable substrate to the fixed substrate side using electrostatic attraction generated by applying a voltage between the diaphragm and the fixed substrate.
Incidentally, in the Fabry-Perot filter disclosed in JP-A-2003-185941, a configuration is adopted in which the bending of the protruding portion formed in a larger thickness than the diaphragm is suppressed by bending the diaphragm to the fixed substrate side when changing the size of the gap between the fixed mirror and the movable mirror. In practice, however, if the diaphragm is bent, the protruding portion is also slightly bent, and the movable mirror provided in the protruding portion is also bent. Therefore, in the wavelength tunable interference filter disclosed in JP-A-2003-185941, when the size of the gap between the fixed mirror and the movable mirror is reduced from the initial state where the gap between the fixed mirror and the movable mirror is largest, that is, when light extracted by the wavelength tunable interference filter is shifted from the long wavelength side to the short wavelength side, the full width at half maximum is increased by the influence of the bending of the movable mirror. As a result, a resolution is reduced.
On the other hand, the reflectance of the fixed mirror or the movable mirror changes with a material of the fixed mirror or the movable mirror. In general, when a reflective film is formed of a metal material, the reflectance increases from the short wavelength side toward the long wavelength side in a visible region.
Accordingly, when the light extracted by the wavelength tunable interference filter is shifted from the long wavelength side to the short wavelength side as described above, there is a problem in that the resolution becomes more uneven due to the influence of the bending of the movable mirror and the influence of the reflectance characteristics of the fixed mirror or the movable mirror.